How obvious was the problem?
Quote:
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Postaccident inspection of the signal equipment in the train control room at the Fort Totten station identified the B2-304TR electromechanical vital relay for track circuit B2-304 to be out of correspondence with the physical location of the accident trains. The track relay was energized with both accident trains still shunting the occupied track circuit. After removal of the accident wreckage, track circuits in the vicinity of the collision were tested using a 0.06 ohm and a hardwire shunt. Track circuits B2-344, 336, 328, 322 and 312 were tested with a single 0.06 ohm shunt at three different locations, at the transmitter end, in the middle and at the receiver end of the track circuit. All track relays de-energized in response to the detection of each shunt. Track circuit B2-304was then tested and detected a 0.06 ohm shunt at the transmitter end of the circuit. The track circuit however failed to detect a 0.06 ohm or a hardwire shunt in the middle of the track circuit.
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With two crashed trains on the track, the signalling hardware still reported the track empty. The reason for crash was immediately obvious to all Metro managment. Later tests showed signals would detect trains at both ends of the 738 foot track. But not in the middle.
The report then goes on to explain why maintenance people needed high tech help. But high tech assistance was not called. Instead, they just kept replacing parts on wild speculation - shotgunning.